From what I understood was, he was separating from Misaki so that he could learn how to love her for real, and not just play along with the contract or not being as serious as he could be about it. That and maybe Misaki will mature and become slightly less dramatic (although that is her funny aspect)
I think secretly inside he might have still been slightly doubtful. Doesn't mean he doesn't care about her, but he wants to be more independent so he can feel it in all his being perhaps? From what I read last, I figured they might meet again at some point. She did say she would be waiting.
Since it was realistic, and it hinted and them being together again, I thought it was an interesting ending.